Particle analyzing method and apparatus employing multiple apertures and multiple channels per aperture

ABSTRACT

Disclosed is an improved method and apparatus for analyzing particles by the Coulter principle of employing an impedance responsive detecting aperture through which pass particles in suspension. Employed herein are a plurality of logically parallel detecting apertures, preferably of different microscopic sizes, each aperture feeding circuitry which is subdivided into a plurality of channels, each responsive to a different narrow subrange of particle size. By time and volume related elements, there is generated an output voltage which is proportional to particle volume per unit time over the entire particle system; hence, statistically valid data is available at all times during an analysis run, even in the event of a malfunctioning blockage of an aperture.

United States Patent Wallace H. Coulter Miami Springs;

Walter R. Hogg, Miami Lakes, both oi, Fla. 823,743

May 1 2, l 969 Sept. 7, 1971 Coulter Electronics, Inc.

Hialeah, Fla.

Continuation-impart of application Ser. No. 527,146, Feb. 14, 1966, nowPatent No. 3,444,463, dated May 13, 1969.

[72] Inventors [2i Appl No. [22] Filed [45] Patented [73] Assignee {54]PARTICLE ANALYZING METHOD AND APPARATUS EMPLOYING MULTIPLE APERTURES ANDMULTIPLE CHANNELS PER 235/92 PC; ass/35,40, 102, 20s

Primary Examiner-Michael J. Lynch Attorney-Silverman & Cass ABSTRACT:Disclosed is an improved method and apparatus for analyzing particles bythe Coulter principle of employing an impedance responsive detectingaperture through which pass particles in suspension. Employed herein area plurality of logically parallel detecting apertures, preferably ofdifferent microscopic sizes, each aperture feeding circuitry which issubdivided into a plurality of channels, each responsive to a difi'erentnarrow subrange of particle size. By time and volume related elements,there is generated an output voltage which is proportional to particlevolume per unit time over the entire particle system; hence,statistically valid data is available at all times during an analysisrun, even in the event of a malfunctioning blockage of an aperture.

SHEET 2 0F 3 PATENTED SEP 7 IHTI PATENTED SEP 7 I97! SHEEI 3 UF 3.PARTICLEANAIJYZING METHOD AND APPARATUS EMPLOYING MULTIPLE APERTUIRESAND MULTIPLE CHANNELS PER APERTURE CROSS-REFERENCE TO RELATEDAPPLICATIONS This is a Continuation-in-part of our copending applicationSer. No. 527,146, filed Feb. 14, 1966, entitled Particle AnalyzingApparatus and Method Utilizing Multiple Apertures," now U.S. Pat. No.3,444,463 issued on May 13, 1969 and hereinafter referred to as thefirs-t" copending applica tion.

Cited hereinafter as the second" copending application is Ser. No.410,882, filed Nov. 13, I964, and entitled Automatic Particle Size DataConverting Apparatus."

This and the cited two copending applications are assigned to CoulterElectronics, Inc. manufacturers of apparatus, including particleanalyzers, known throughout the world by the trademark Coulter Counter."Such apparatus and methods for utilizing the Coulter principle arediscussed herein with reference to the Coulter apparatus and Coultermethod.

BACKGROUND OF THE INVENTION This invention relates generally to particleanalyzing apparatus and method especially the type which use the Coulterprinciple described in U.S. Pat. No. 2,656,508, and more particularly isconcerned with apparatus and method which utilize a plurality ofapertures, each aperture having a plurality of channels for obtaininginformation.

The cited first copending application describes and claims apparatus anda method operating in accordance with the basic principles used in theapparatus of this invention. A fluid suspension of particles is passedthrough a plurality of apertures simultaneously or consecutively or inconsecutive groups, each aperture having its own aperture current supplyand its own detector to provide one channel for the signals produced bythe respective aperture. Certain advantages are gained by the use ofmultiple apertures, such as savings of time, better statistical data,etc. Such advantages are inherent in this invention as well. Likewise,the apparatus of the first copending application includes a vote circuitwhich identifies and can reject automatically, information derived froma channel which is erroneous because of blockage of the apertureproducing the signals-of that channel. The disclosed embodiment of thisinvention uses such vote circuits, but, as will be seen, a feature ofthe invention substantially decreases, if not completely eliminates theneed for such circuits.

The structure of this invention is of the special kind that usesapertures of different size to give statistical information of thedistribution of particles in a system having particles of widelydifferent sizes. Since this is a special case of the basic concept, adiscussion of the problems involved in obtaining distribution data forthis kind of a system will be in order, although to some small extentrepetitious of the discussion in the first copending application.

The second copending application describes means for reducing particlecount information gathered from a plurality of channels, all coupled tothe single aperture of the apparatus. The characteristics of an ordinaryso-called industrial system of particles are fairly well known. Thesesystems would include slurries,'dusts, powders, emulsions, and the likeof a vast gamut of materials. These characteristics are generally asfollows:

1. Most importantly, the dynamic range of particle size is very great,compared, for example with ordinary blood cells or biological particles.The smaller particles, not uncommonly, may be thousands of times smallerthan the larger particles.

2. The occurrence of the particles, that is their distribution sizewisein the sample follows a general pattern in which there are anexceedingly larger number of smaller particles than larger particles Forexample, there may be tens of millions of particles of the order ofseveral microns in diameter compared to a few hundreds of particles ofthe order of several hundred microns in diameter.

3. Notwithstanding the second characteristic described above, thegreater volume or mass of particulate material in most types of samplewill occur somewhere near the center of the range of particle sizes,i.e., is contributed by the middle sized particles.

In the classical methods of particle study, Stokesian methods involvingsedimentation were used to obtain the data of size distribution andmass. These methods may be categorized as gross in concept because largequantities are weighed, settled, dropped, sieved and/or spun to givethe, required data. As opposed to such methods, the Coulter apparatushas permitted the electronic counting of particles one by one,accomplished by passing the suspension at a high speed through amicroscopic aperture. The Coulter apparatus has become widely used inmany particle categories formerly handled by Stokesian methods.

There is no need to explain the Coulter principle at length, other thanto state that where an aperture is provided in an insulating wall, and afluid suspension of particles is flowed through the aperture from afluid body on one side of the wall to a second fluid body on the otherside, each time a particle passes through the aperture it will displaceits own volume of fluid and thereby change the impedance of the fluidcontained in the aperture as measured between the electrodes used tomake connection to it. This presumes that the current-carryingcapabilities of the fluid and the particulate matter are different. Ifthere is an electric current also passing through the aperture, one maygenerate electric signals as a result of the concomitant changes inimpedance, and by coupling a suitable detector commonly as a simpleamplifier to the respective bodies of fluid, normally through the sameelectrodes that provide the connection to the aperture current source,one may obtain substantial electric pulses, each representing a passageof a particle. The duration of each pulse is equal to the duration ofthe particles stay in the aperture, and if operating conditions areproperly chosen, the amplitude is proportional to the total volume ofthe particle, substantially irrespective of its shape.

This should be contrasted with optical scanning which responds tomaximum cross sectional area of the particle perpendicular to thedirection of light, which varies widely for irregularly shaped particlesdue to their unpredictable orientation.

Counting and sizing by Stokesian methods have resulted in characteristiccurves which describe a particle system, and although the Coulterapparatus has capabilities far exceeding those of the Stokesianapparatus, the data gathered from such apparatus for the most part arerequired to be converted or reduced into information in the classicalform. Persons working in the particle field have become accustomed tosuch form and base their actions on interpretations thereof.

Two characteristic curves are used to express particle distribution inthe classical form. One curve, called the differential curve consists ofa plot of the distribution of particulate material in the variousranges, the horizontal axis being particle size and the vertical axisbeing, volume of particulate material existing in any given range ofparticle sizes. The second curve, called the integral curve, givespercentage of particulate material above a stated size. The horizontalaxis of the integral curve is also particle size, but the vertical axisis volume or percent of the total mass of particulate material above anysize. The differential curve is usually somewhat bell-shaped, while theintegral curve is a reverse S. Obviously, the percent point at the topof the integral curve will represent the smallest particle, and the 0percent point of the same curve will represent the largest particle. Inboth cases, since the size range of particles is great the horizontalaxis is usually logarithmic. One curve may also be converted into theother.

The Coulter Counter has gone a long way in providing information to beused in producing these curves which are so important to theunderstanding of those working in this field, but

its capabilities and potential have only been partially utilized.

The invention contemplates a vastly increased use of the capabilities ofan apparatus which operates on the Coulter principle as a result ofwhich many advantages are achieved not capable of achievementheretofore.

Prior counting and sizing apparatus of the Coulter type utilized asingle aperture for obtaining the information needed to describe aparticle system. It was desired to extend the range of particle sizescovered by the aperture to derive as much information as possible fromthe aperture. Various techniques attended such attempts, all of whichwere directed toward the obtaining of the best quality and the maximumamount of information.

The use of a single aperture of a compromise diameter decreasedsensitivity of the aperture to the smaller particles and increasedcoincidence loss for a given particle concentration. It also introducedan error in linear response to particles greater than or percent of theaperture diameter. It usually required multiple dilutions to get thebest results, including scalping or decanting to prevent large particleblockages. Dividing the sample runs into two ranges with differentapertures alleviated some of the problems arising because of the verywide range of particle sizes, but prior art has taught that the use ofmore than one aperture is a last resort, and the maximum span of eachaperture was usually demanded.

SUMMARY OF THE INVENTION The invention herein does the opposite of whathas been attempted in prior applications of the Coulter apparatus.Instead of extending the range of any single aperture, this invention isbased on the use of only the smallest feasible range capability of anaperture.

Among the objects of this invention are: obtaining a saving of time inrunning a sample; eliminating the problems involved in scalping ordiluting; making unnecessary prior knowledge of the distribution andpopulation of the type of particle system being studied; obtaining avast increase in accuracy and in'the quantity of data which may beobtained on a given sample run; improving the reliability of theapparatus and in addition decreasing the likelihood of blockage; makingpossible the acquisition of valid data even when a blockage occurs; andin general improving greatly the overall quality and statistics inpractically every respect of the information obtained.

In using the Coulter apparatus, one device described in said secondcopending application provided structure for reducing the data beforepresentation, so that the output of the device enabled the constructionof the integral and differential curves of the particle system directlyfrom the readouts. A plotter suitably connected could draw the curves.This apparatus used a single aperture to make a sample run, the spectrumof particle sizes being divided into a plurality of consecutive rangeseach providing the signals to a separate channel by means of suitablethreshold circuits. The ranges were chosen to have a progressiverelationship in accordance with a known function, such as, for example,a two-to-one relationship between contiguous ranges based upon theaverage size of the particles in the respective ranges. An equal volumeof suspension was scanned for each range in any given sample run. Theresulting counts were operatedupon before deriving the final data, inaccordance with a progressive function equal to that used to divide thespectrum into ranges. The values in the resulting series were directlyproportional to the total volume of particulate material in eachrespective range.

Thus, the data for constructing the ultimate integral and differentialcurves were available, albeit with the attendant disadvantages of usinga single aperture. This included the loss of any usable data uponblockage of the single aperture. Use of more than one aperture requiredtwo dilutions, and two independent runs, but this gave rise to addedblockage problems. Scalping could not'be avoided.

The invention has as another object the provision of apparatus intowhichone may readily construct the principles of the data reduction structuredescribed above, without unduly complicating the apparatus.

In using a plurality of apertures, it should beunderstood that in thelower ranges it is not essential that the same amount of suspension passthrough the apertures for a good statistical sample as in the case ofthe upper ranges. One may therefore decrease quite substantially thechances of .bloekage by scanning only a minute sample in an aperture ofhigh sensitivity, and obtain excellent results. The apparatus of theinvention enables this to be done automatically and with properrelationship to the other data being gathered by the device.

The invention provides output information for each channel in the formof a voltage which is proportional to volume per unit time, representingvolume of particulate material in that channel or of that size particle,but considering the entire particle system. Thus the points of theintegral curve are obtained directly. Since this information is beingproduced at all times, even when blockage occurs, the informationobtained up to that time on any group of channels produced by theaperture which just blocked is still valid, albeit statisticallyrepresentative only of the amount of sample scanned.

The structure of the invention accomplishes the above by using twoelements in each channel controlled from the same voltage referencesource. One element furnishes volume information and the other time. Thevolume information is provided by integrators that are slowlyaccumulating charge through capacitive pump circuits driven by theparticle pulses. A scale factor is applied to the pump circuits by thevoltage reference source and size of pump capacitors. The timeinformation is obtained from an integrator which runs continuously andaccumulates charge from the same reference voltage source. Signals fromboth integrators of each channel are applied to a multiplier, but thetime integrator signal is first operated upon by a reciprocal computerso that the multiplier output is of voltage representing particle volumerelative to time. Since the flow rate through each aperture is known,the multiplier output may be calibrated in terms of number of particlesper unit volume of sample suspension which is the required form.

Many advantages and objects which are not set forth above will becomemore apparent as a description of a preferred embodiment of theinvention is set forth in detail, in connection with which there isillustrated in block diagram form a portion of a typical particleanalyzing apparatus constructed in accordance with the invention, toenable an understanding thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A and FIG. 1B are the left andright halves, respectively, of a block diagram of a portion of aparticle analyzing apparatus constructed in accordance with theinvention, the portion illustrated relating only to the channels of oneof a plurality of apertures included in the apparatus.

FIG. 2 is a placement diagram showing the relationship between FIGS. 1Aand 1B.

FIG. 3 is a front elevational view of a structure which may be used toprovide the scanning system for the entire apparatus, including meansfor functionally supporting six apertures.

FIG. 4 is a sectional view taken through the structure of FIG. 3 alongthe line 4-4 and generally in the indicated direction.

FIG. 5 is a diagram of a typical pump circuit of thetype used in theapparatus.

FIG. 6 is an enlarged sectional view along the line 6-6 of FIG. 4.

DESCRIPTION OF A PREFERRED EMBODIMENT The apparatus of the inventionutilizes a plurality of apertures, each of which is chosen according toa sequence designed to use a high degree of the capabilities of theaperture, considering sensitivity, coincidence, flow rate and theprobability of clogging. The apertures may be mounted in a plurality ofaperture tubes of the type known and all tubes immersed in a containerof the sample for a static determination, or these apertures may belocated in a conduit or pipe through which there is flowing a continuousstream of the sample suspension. In either case, the structures may takemany dif ferent forms. One such form is shown in FIGS. 3 and 4.

Each aperture is connected into the system in a manner to provideindependent flow-including means to permit the sample to be carriedthrough the apertures consecutively or simultaneously or in consecutivegroups. Means may be provided to trigger the operation of one flowinducing means upon the completion of operation of the preceding one.Each aperture has an independent current source and an independentdetector, such that care must be taken electrically to isolate thedownstream ends of the apertures to prevent interaction between them.There will be an electrode in the downstream fluid for each aperture anda single common electrode in the upstream body of fluid, usually atground potential.

In an apparatus which is intended to provide an output representingnumbers related to the amount of particulate volume in the respectiveranges of a particle system, the device described in the secondcopending application identified above which used a single aperture wassomewhat limited. Although data reduction was accomplished, it isapparent that the same volume of sample passes through the aperture forany sample run to give information for all ranges. The amount ofmaterial in each size range varies considerably, as pointed out, and itis not necessary to pass the same volume of suspension through theaperture for a good statistical count in heavily populated ranges as insparsely populated ranges.

In the apparatus of this invention, the flow time in heavily populatedranges may be decreased by any suitable factor to give a count which maybe then multiplied by the factor to give the total relative count. Thisdecreases the chance of clogging by the same percentage. Furthermore,since there is to be an operation made upon the count to provide thedesired data reduction, such operation could as easily be fonned bymeans of changing the time for the sample flow, either alone or incombination with some other means.

The apparatus, through the use of multiple apertures, may utilize rateof flow, size of aperture, and in addition, variation of constants ofthe circuits to achieve the desired operation upon count, and hence inthis respect alone, is a substantial improvement upon the prior singleaperture apparatus. In addition, the need for scalping and redilution iseliminated.

The particular apparatus which is discussed herein is one in which thereis a plurality of channels for each aperture, so that the rangerepresented by the chosen limits for any aperture may in turn be dividedinto what may be called subranges, each of which produces signalspassing through a single electrical channel. Furthermore, means areincluded in the apparatus for taking only as much data as absolutelynecessary including means for arriving at a correct measurement even ifan aperture clogs, the latter event being less likely to occur in thisapparatus than in previous devices.

In the practical structure, only a portion of which is illustrated inthe figure, there are 25 channels of information, one for each sizerange of particles. This number has been chosen in order to accommodatea large and yet practical majority of particle systems which are knownto be measurable by the Coulter method. The operation of the apparatusis arranged to be based upon differences between channel sizesconsisting of successive factors of two, as explained in connection withthe structure of said second copending application, so that startingwith the smallest channel, the average particle size in the next channelwill be two times as large, in the next channel four times as large asthe smallest, in the next eight times as large as the smallest and soon. Of course, any desired factor may be used within the above designcriteria, or any other method of choosing levels, even without the useof some function of interrelation, but in the latter case, of coursethere would be no partial reduction of data.

The choice of aperture sizes and particle size ranges described aboveresults in an important, unexpected, and previously overlooked benefit,namely, the ability to accept, without further adjustment ormanipulation, particulate systems of any nature, whether broad ornarrow, consisting mostly of large or small particles, that is, whetherthe bellshaped curve is broad or narrow at the center, whether the peakoccurs right or left of center, and so on. Suitable analog clock meansare used to permit the apertures to pass fluid suspension for only theminimum time that it is almost certain a good sampling will be obtainedwhile clogging is unlikely, considering that particular size ofaperture. The data reduction is performed in part by this decrease insample as the particle size decreases. Even if clogging does occur, datawhich is taken may be divided by the elapsed time to make it usable, butperhaps with less statistical reliability.

In the drawings, the FIGS. 1A and 13 actually comprise parts of a singleillustration. This is intended to show a single range, defined by anaperture, and three subranges or channels within the principal range. Aswill be seen, from the numbering of the components, it is understoodthat this in turn is a small part of a large apparatus, but thecomponents of the ap' paratus are repetitious in nature, the whole beingdesigned to give a thorough statistical analysis of a particle system.

The block it) which is identified as A4! is one of six apertures, forexample, which are used by the apparatus. Accordingly there are otherblocks which would be displayed above the portion shown which representthe larger apertures, and which would be identified as Al, A2 and A3.Likewise, the portion below the illustrated portion would have blocksrepresenting the smaller apertures identified as A5 and A6. In order toillustrate the nature of the device, the sizes of the six aperturesmight be chosen as A1 560 microns in diameter A2 280 microns in diameterA3 microns in diameter A4 70 microns in diameter A5 30 microns indiameter A6 20 microns in diameter These apertures each represent arange of particle sizes, and were chosen to afford the best statisticalinformation in the ranges which will be covered by each. The largestaperture, which would be A1 might be divided by suitable thresholdcircuits into nine subranges and thus provide information on ninechannels; the next four ranges might each have three channels, and thesmallest range might have four channels. The channels for the extremesof size range typically include a very small percentage of the totalparticulate material and hence do not justify the accuracy obtained byhaving only three sized subranges per aperture. Thus, there would be atotal of 25 channels provided by six apertures.

For the purpose of conforming to the relative sizes of the channels,which will be providing a partial reduction of data, it will be notedthat the apertures are chosen so that the diameters decrease fromaperture to aperture by very nearly a factor of two.

The amount of sample which will be moved through the respectiveapertures, according to the said first copending application which ismentioned above, will be equal in simple apparatus, but for best resultsshould vary in accordance with the size of the particles studied. Thus,since the smaller apertures will be primarily used for obtaining thesignals from small par ticles, which are typically extremely numerous,only a fraction of the amount of sample taken in the larger apertureswill be driven through the smaller. A structure for accomplishing thiscould be a micrometer head syringe operated by a constant speedsynchronous motor. The motor is clutched to the syringe by a high speedmagnetic or other type of clutch, and a suitable timing device, such asa light interrupter disc with light source and photocell may give adigital or analog measurement of the amount of movement of the syringe,to be related in other parts of the-circuit with other components of theapparatus.

This fluid driving device whether operated by pump or suction may be thesame for several apertures, those with greater sampling time andrequiring passage of greater amounts of sampling fluid being associatedwith other fluid moving devices.

In FIGS. 1A and 1B, the fluid moving device is the block 11, called asuction device 04. Each aperture will have its own suction device. Thepractical structure of FIGS. 3 and 4 does not illustrate fluid movingmeans. Some fluid moving means are illustrated in U.S. Pat. Nos.2,869,078 and 3,015,775.

Since the components described will be duplicated, only the one seriesassociated with the aperture A4 will be described. The aperture A4 likethe others, has its own aperture current supply source identified by thedesignation R4 and the block 12. The signal from the aperture A4 isamplified to a useful level by the amplifier 135 shown in block 13.Output from the amplifier B5 is applied by way of the connections 14,15, 16 and 17 to the blocks 18, 19, 20 and 21, respectively, theseblocks being identified by the labels C16, C17, C18 and C19,respectively; and threshold levels are built into the blocks in such amanner that there is a factor of two between each threshold level allthrough the apparatus. The threshold circuits between contiguousaperture groups have the identical level. Thus, the next thresholdcircuit above C16, which is the smallest in the group served by theaperture A3 and is shown in the drawings, is C15, identical in level toC16. Likewise the first threshold circuit C20 of the next smaller group,is identical in level to the level of the threshold circuit C19. Betweeneach threshold circuit, therefore, there is a subrange of particleswhose average volume changes from channel to channel by a factor of two.

Two types of Coulter electronic counting and sizing apparatus in usehave different kinds of threshold circuits, one of which has a singlevoltage level to pass only pulses which exceed that level, and the otherof which has two voltage levels, so that only pulses whose amplitudesfall within the defined window will be passed. The first type ofthreshold circuit is an integral type, and the second is a differentialtype. A differential type typically comprises two integral typesinterconnected by veto logic circuitry. These kinds of threshold areboth useful in accumulating and reducing data obtained by CoulterCounters as the Coulter apparatus is known. In the drawings, thethreshold circuits identified as C are of the integral type, hence thereis one more threshold in each range than the number of eventual channelsto define size limits. Ob viously differential threshold circuits couldbe used.

The threshold circuits throughout the apparatus are connected in pairsto veto logic circuits designated D. The threshold circuits C16 and C17are connected to the veto logic circuit D13. The threshold circuits C17and C18 are connected to the veto logic circuit D14. The thresholdcircuits C18 and C19 are connected to the veto logic circuit D15. Theveto logic circuits are designated by reference characters 22, 23 and24. The veto logic circuits define the limits of channels by preventingany pulses whose amplitudes do not fall between the levels establishedby the two thresholds feeding each veto logic circuit from eliciting anoutput from a veto circuit. Thus, each pair of threshold circuits andtheir connected veto logic circuit form a differential threshold circuitdefining a window.

The outputs from the veto logic circuits appear at 25, 26 and 27 andmust pass through the AND gates E13, E14 and E in order to affect thepump circuits F13, F14 and F15, respectively. The AND gates are numbered28, 29 and 30 while the corresponding pump circuits are numbered 31, 32and 33. The AND gates are opened and closed at various times by thesignals appearing at the control line 34, and thus determine the timesthat pulses will be fed through the pump circuits to integrator circuitswhere they are accumulated. Integrator circuits are identified by theletter G and the blocks are numbered 35, 36 and 37. During a count, avoltage exists on the line 34 so that signals from the veto circuitsD13, D14 and D15 will pass through the gates.

For any given aperture such as the aperture A4, particles of differentsizes are counted, sorted according to their appropriate size levels orranges and fed to the corresponding integrators for a measurable lengthof time. Pump circuits F13, F14 and F15 pass charges to the followingintegrators at rates determined by the DC reference to which their pumpcondensers charge, this reference being supplied at the line 49 from theDC reference K (FIG. 13). T 7

As previously explained the pump circuits identified by the letter Freceive pulses from the AND circuits and transmit charges to theintegrators G13, G14 and G15 where they are accumulated. Now each pumpcircuit includes a capacitor which is to be charged upon the arrival ofpulse via path 57, 58 or 59 to the voltage impressed on path 49 by DCreference 74 of FIG. 1B, the charge being pumped to the integratorconnected to that pump circuit. The amount of charge that any given pumpcircuit will transmit to its integrator for a given pulse is determinedby the reference voltage derived from the line 49 and the capacitance ofthe capacitor. Reference may be had to FIG. 5 for an example of pumpcircuit. The incoming pulses appear via the path 57, having beentransmitted from one of the AND gates E13, E14 or E15. Pulses operate aswitch 181, which has the effect of connecting the capacitor 182alternately between the reference voltage supply means K and ground.Each time the switch 181 connects capacitor 182 to the reference voltageK, it charges up to this voltage due to current flowing through diode184. When the switch reverts to its normal position, the diode 184blocks flow of current to ground and the diode 183 passes substantiallyall the charge to the integrator. The switch 181 may be a transistorizedcircuit in which transistors are switched between conducting andnonconducting conditions upon receiving pulses from the AND circuitpreceding.

It will be seen that if the reference voltage from the DC Reference K at74 is increased, it will require fewer pulses to cause any given voltagelevel to be reached by the integrator into which the pump istransmitting charge. Assuming a constant rate of arrival of pulses, anda given reference voltage, the integrator will reach any predeterminedlevel after a given time has passed. By increasing the reference voltagethat time can be decreased.

It should be recalled that the integrators G13, G14 and G15 are eachaccumulating information which represents volume of particulate matterfor each channel.

The current supply R4 at 12 and the fluid moving device Q4 at 11 haveconnections to a control binary circuit P9 which is shown at 39 on theleft-hand side of FIG. 1A. This latter circuit is usually in the form ofa set-reset flip-flop (or RS flipfiop) whose purpose is to start andstop the counting of the entire range defined by the channels of A4.There is a start" line 40 and a stop" line 41 and a connection from thecontrol binary P9 at 42 through a delay circuit 44 labeled S3 and a line43 to another control binary P3 shown in block 45. This same circuitryis duplicated for each aperture.

In this apparatus, counting in the several ranges may be donesimultaneously for all apertures, consecutively, or in groups. Ifsimultaneously, the line 40 originates in a suitable common control forall control binaries connected to the apertures, which may manually orelectrically furnish a start signal to all aperture scanning systems. Ifconsecutive, either individually or in groups, the signal may come as aresult of some prior event. In this embodiment, the start signal comesfrom the completion of counting in the previous contiguous range. Thecontrol binary P2 shown as block 62 at the bottom of FIG. 1A isequivalent to the binary P3. When counting is completed in the priorrange, a stop signal on line 63 will change the state of the binary 62causing it to remove a voltage existing on the line 64. This line 64connects with the line 40 through a trailing edge detector 66 whichconnects with the control binary P9 so that the state of this binary ischanged. The scanning is started by this change of state of the binaryP9 and likewise it produces a signal output 42 passing through the delaycircuit S3 at 44 and the line 43 to the control binary P3,

changing its state. The delay circuit P3 is to obviate switchingtransients caused by starting the scanning operation. The change ofstate of the control binary P3 places a signal on the line 3d and itsextensions, thereby providing one input to the AND gates E13, E14, E15and E23 at 77 in FIG. 113, so that these gates are receptive to signals.Otherwise, no signals can pass these gates. The voltage on the line 34does not affect the control binary P at 101 of the next range until itis removed by control binary P3, at which time the trailing edgedetector 103 applies the necessary trigger to initiate the same cycle ofevents in the next range.

When the counting in the aperture A4 has been completed, there will be asignal at 65 as well as at 41. The signal at 65 changes the state ofbinary control circuit P3, removing the voltage on the line 34 and itsextensions and blocking the AND gates 28, 29 and 30. It also changes thestate of the control binary P10, shown in block 101 and this starts thecounting in the next channel.

The count in the channels of aperture A4 will continue until somepredetermined number of particles is counted on one of the channels ofthe aperture Ad, unless halted prematurely by approaching saturation ofany integrator by OR gate J10 and threshold circuit C40 or at apredetermined time as set by threshold C io, or upon the arrival of apulse via line 67 indicating a pluggage. This number of particles iscontrolled by the threshold circuit C33 shown in FIG. 18 at 46. This'threshold circuit, when operated by reaching the proper number which hasbeen set into its circuit, that is voltage, produces a trigger signal at47 that is applied to the OR gate J4. The outputs from this gate are 65and 41. Output 65 triggers binary P3 as explained above. Output d1triggers control binary circuit P9 which stops the operation ofscanning.

Since the net effect of the quantity of sample scanned, the size of theintegrator capacitors and the size of the pump capacitors in the pumpcircuits F13, F14 and F are adjusted to be proportional to the volumesof the particles represented by each channel, the information stored inthe integrators G13, G14 and G15 is proportional to the volume ofmaterial in that size range. This information is continually passed toreadout circuits, as will be described, by suitable connections 83, 84and 85.

It is desired to stop the counting when a given number has been reached.In order to specify the desired statistical accuracy, or coefficient ofvariation, it is necessary to take the relative size information fromthe three channels of the aperture Ad by the use of simple DC amplifiersor voltage dividers H6 and H7 shown at 50 and 51 which multiply ordivide by 2 or for the inside and outside channels, respectively. Notethat the integrator 615 has its output 52 connected to the OR gate J33,the integrator G14 has one output 53 connected through the voltagedivider H7 to the line 5% which leads to the input of the OR gate J33and the integrator G13 has its output 55 going through the voltagedivider 1-16 to the line 56 which is another input ofthe OR gate J33.This latter is numbered 60.

While the circuits J10 and J33 at 97 and 60, respectively, designated asOR gates comprise as many diodes as they have inputs and have the samecircuit diagram as OR gates, their function is somewhat different fromthe function generally delegated to OR gates. These circuits make use ofthe fact that the output voltage of an OR gate will equal the largestinput voltage. It is thus an analog as well as a logical element.Accordingly, any one of the channels in the range may raise the voltageat 61 to a value which will reach or exceed the threshold level in thecircuit C33. When this occurs the count is shut off in the mannerdescribed through the OR gate J4. J4 performs a logical function only.Note that any of the inputs to the OR gate J ll will shut off the count.Besides the input 47, there is one at 67 which comes from a debris alarmT45 shown at as driven in some manner by the output of the amplifier.For example, the debris alarm T4 may detect low frequency componentscaused by the presence of debris to give an audible or visual warningand a signal which shuts off the counting. Such a device is described inUs. Pat. No. 3,259,891 issued Ill July 5, 1966 to the applicant herein.Likewise, the threshold circuit C40 at 69 may be adjusted to some levelwhich represents a condition just short of saturation of the circuitcomponents connected to the inputs 70, 71 and 72 of the OR gate J10 andwhich will serve to stop the counting. The path 73 to the OR gate M isprovided with the separate, adjustable threshold circuit C46 at 99 inorder to give the operator control over the counting time.

The threshold circuit C33 like all of the other threshold circuits inthe apparatus is variable over a substantial range, such as for example8] to l, which provides a 9 to 1 choice ofsigma which could beselectable by a suitable control on the threshold circuit.

At the same time that information is being gathered related to thevolume of particulate matter in each channel, a simulated timing deviceis being operated. In the particular circuit this timing device is inthe form of a simple integrator or clock integrator G28, shown in FIG.113 at 76. This integrator accumulates charge only from one source,namely the DC reference K by way of the line 75 and the switch E23,shown at 77. Since the switch E23 and the AND gates E13, E14 and E15 areall operated by the same control binary P3 via path 34, they all operatefor the identical time interval and hence the voltage to which the clockintegrator G28 charges is a measure of the time during which rangeparticulate volume accumulations are made in the integrators G13, GM,and G15.

The DC reference K serves all of the pump circuits and clock integratorsof the apparatus through lines 49 and 75. The voltage from the clockintegrator G23 is transmitted through a reciprocal computer L I shown at79 to each of the multipliers M13, M14 and M15 designated by thecharacters 80, 81 and 82. Since the volume information from theintegrators G13, G14 and G15 is also being transmitted to themultipliers by the lines 83, 5M and 85, respectively, the operationperformed in each multiplier is to combine the voltage representingvolume for a particular channel and the reciprocal of time. The resultis volume per unit time. Since the flow rate through each aperture isknown, this is directly convertible to particulate volume per size rangeper unit volume of suspension. This output at 89, 911 and 91 is thedesired information which is always valid, irrespective of how muchsample has passed through the aperture and for how long. Accordingly,stopping the pulses from the aperture A l at any time before the desiredcount is reached will not affect the information gathered up to thattime. The only question will be the statistical quality.

The control exerted upon the integrators G13, GM and G15 was describedabove in connection with the pump circuits F13, F1 1 and F15. By havingthe same voltage reference source control the clock integrator G28, theoutput information of volume relative to time is obtained. The voltageof the DC reference could be fixed, of course, to produce the resultsdescribed. Greater flexibility is achieved, however, by making thevoltage of the reference K variable. Referring to FIG. 5, variation canbe seen to increase or decrease the number of pulses required to causethe integrators G13, G14 and G15 to reach any predetermined level. Thesame variation affects the clock integrator G23. Although it isindependent of the number of pulses arriving, it depends upon the valueof the reference voltage for its charge. Decreasing the referencevoltage increases the time for the clock integrator G23 to charge. Thereciprocal of this charge when multiplied by the value of the volumeintegrators will therefore always give the same value of volume withrespect to time.

The voltage of the source could be variable from a low valuesay 12.5volts to 200 volts and this could be related to values of sigma. Lowvoltages would establish small unit charges and cause the volumeintegrators to accumulate charge at a slow speed thereby permitting thestorage of many times more unit charges than if the reference voltagewere high, before saturating. The clock integrator would also be sloweddown. As indicated, the relationship would not change,

but the amount of sample measured would increase with greater resultingaccuracy. If the aperture clogged before the end of the run, themeasurement would stop and the full statistical accuracy not obtained.it would still preserve the same relationship.

if the voltage of the reference K were raised, tee reverse would takeplace. The result could be a saving of diluent and increased freedomfrom clogging at the expense of lesser statistical accuracy.

This adjustment is a great tool for flexibility and is quite simple inconcept.

The reciprocal computer L4 at 79 transmits the signal from the clockintegrator to all multipliers 80, 81 and 82. The multipliers areaccordingly performing the operation particle count multiplied byrelative cubic volume divided by time.

This quantity is fed by the read-outs N13, N14 and N15, shownrespectively at 86, 87 and 88. It may be described as the mean particlevolume multiplied by the particle count in each channel per unit time.Since time is proportional to the amount of sample volume passed, thisyields as an expression which may be written k(pv) (pc)/sample volumetotal particle volume per channel/sample volume where k is someconstant, pv, is the means particle volume of the channel in questionand pc is the particle count per channel. The voltage output at 89, 90and 91 represent these quantities. These quantities may be fed bysuitable lines to a summing matrix 92 along with the other values fromthe other channels, the output used to draw a curve in a suitableplotter 93 giving directly percent above stated size, or any other curverepresenting the values.

To conclude relative to the nature of the voltage output, since eachline at 89, 90 and 91 carries a voltage which is proportional to thevolume of material in the window represented by that channel or subrangeof the range encompassed by the aperture A4, the information which hasbeen achieved is the ultimate desired by the particle worker to use inthe construction of his classical curves. The apparatus has weightedeverything in accordance with the time run, size, and so on, havingperformed all of the data reduction required to give volume ofparticulate material for the particular size of particles in that range.

The components of the apparatus described are capable of beingconstructed through the use of well-known electronic techniques. It isbelieved that the identification and described functions should besufficient for those skilled in this art.

With respect to the scanning system, one form of multiple apertureapparatus using six apertures is shown in FIGS. 3 and 4. The apparatusis designated generally 120 and is shown as apparatus for use with astatic sample, but it should be understood that it is capable of beingused with a flow-through or on-stream sample. There is a vessel 121which has a generally circular sidewall 122 with a rear wall 123 and arelatively thick front wall 124. The vessel is preferably made of glassor other insulating material, and the purpose for making the front wallrelatively thick is so that conical sockets may be accurately formedtherein as by grinding. Such a socket is shown at 125. A female fitting126 is mounted on the sidewall 122 in the bottom thereof for drainage,there being a suitable stopcock 127 engaged therein for obviouspurposes.

As stated above, there are six apertures in connection with thisapparatus, only one of which is seen in FIG. 4. This aperture isdesignated 128, and it is formed in a wafer 129 set into the bottom wallof a hollow, generally frustoconical fitting 130 that includes an outercover glass 131 held in place by spring 132, and upper integral inletconduit 133 and a lower outlet conduit 134. On its interior there is afoil electrode 135 electrically connected to a terminal band 136 towhich there is electrically engaged lead 137.

As shown in FIG. 3, this structure described in connection with thefitting 130 is duplicated in each of the other fittings 140, 141, 142,143 and 144. The-purpose of the inlet conduit equivalent to the conduit133 shown in H6. 4 is to enable fluid to be introduced into the interiorchamber of each of the fittings. This chamber is designated 145 in thefitting 130, and it is in contact with the electrode 135. Likewise allof the chambers have this same arrangement.

The purpose of the outlet conduit 134 and its equivalent in each of theother fittings is to permit flushing and removal of air. Accordingly,the large body of fluid 146 will be feeding into six independentsystems. Each fitting has its own electrode equivalent to the electrode135 and its own hot electrical lead. These are designated 147, 137, 148,149, 150 and 151. The common electrode 152 in the vessel 121 has anelectrical lead 153 common to all the other electrical leads.

The construction using the disclike cover glasses, as shown in 131,enables the inner chambers to be cleaned and enables the readyinstallation, repair, etc., of the electrode system. It also enablesillumination and viewing of the apertures, as by elements 154 and 156.

Apparatus which utilizes more than three or four apertures would mostlikely be used in distribution studies so that the aperture sizes wouldbe different. in such an arrangement it would be preferable that someadvantage be taken of the tendency of the larger particles to settle.Statistically, this would not to any great extent change the nature ofthe distribution data if settlement were not permitted to take placeover a substantial period of time. Accordingly, it would be preferredthat the aperture of the fitting 144 be the smallest and the aperture ofthe fitting 140 be the largest with the intermediate graduated. Theorder of increasing size would be in accordance with the level of theaperture and would be 144, 142, 130, 143, 141, 140.

A large drain at the bottom of the vessel could permit large and heavyparticles to drop into the fitting 126 where they could remain despiteefforts to stir the suspension, and upset the true size distribution.Conveniently a poppet valve is seated in the seat 171 formed in thevessel when the stopcock is closed (FIG. 6). The plug 172 has a groove173 which cooperates with the valve stem 174 to permit the valve 170 todrop into seated condition when the stopcock is closed. When the plug172 is rotated to open condition the valve is raised.

The illustrated apparatus and description omit any reference to a votingcircuit which could act to stop the operation of that portion of theapparatus which includes an aperture that clogs. if desired, this couldbe connected using contiguous channels in different ranges as thecomparison basis. Since these channels are preferably of the same rangeof size, the result is common ranges in different apertures which may beused in connection with differential amplifiers to produce signals whendifferent, indicating an abnormality in at least one of the apertures.

In many other respects considerable variation can be made withoutdeparting from the spirit or scope of the invention as defined in theappended claims.

What it is desired to secure by Letters Patent of the United States is:

1. A method for analyzing a particulate system by the use of at leastone passageway through which a sample portion of the particulate systempasses and is detected, said method comprising the steps of:

producing output signals each proportional to the volume of eachdetected particle of said system,

passing said output signals to a plurality of logically parallelchannels, separating said channels to be selectively responsive to saidoutput signals in channels according to an incrementation based upon theamplitude of each said output signal,

accumulating separately and progressively the output signals for eachsaid channel over a determinable period of time,

generating a signal proportional to the reciprocal of said period oftime, and

producing for each channel an electric signal quantity equal to themathematic product of said accumulated output signal and said reciprocaltime signal at any specific time to obtain an electric signal quantityproportional to the total particulate volume per unit time based uponsaid specific time for each channel.

2. A method according to claim 1 comprising the further step of dividingthe volume of said sample portion by said specific time,

said step of producing thereby yielding the ratio of total particulatevolume per channel to volume of said sample portion.

3. A method according to claim 2 comprising the further step ofmaintaining the ratio between sample portion volume and specific timeconstant.

i. A method according to claim 3 comprising the further steps ofterminating the accumulating step upon the accumulation of a presetsignal amplitude in one of said channels.

5. A method according to claim 3 comprising the further step ofterminating the duration of said specific time in response to improperdetection of said particles.

6. A method according to claim 3, comprising the further step ofterminating the duration of said specific time in response to anaccumulation of said output signals upon attaining signal capacity ofany one channel.

'7. A method according to claim 3 comprising the further step ofterminating the duration of said specific time in response to a fixedtime measurement.

8. A method according to claim 1, including sending the output signalsthrough a plurality of the passageways arranged logically parallel, eachpassageway arranged to pass the separated output signals through itsinterrelated channels, and

arranging the incrementation of all said separated output signals in aregular progression based upon particle volume.

9. A method according to claim 8 comprising the further step of enablingsaid accumulating step for the separated output signals for any one ofsaid plurality of channels in relationship to the same accumulatingenabling of the other of said plurality of channels.

Ml. A method according to claim 8 comprising the further step ofregulating the rate of flow of said sample portion through saidpassageways so that such rate is different for each passageway.

Ill. A method according to claim 10 in which said regulating isaccomplished by sizing said passageways according to a mathematicprogression.

12. A method according to claim ti comprising the further step ofarranging the passing of the output signals through the passageways suchthat a narrow amplitude range is sent through each passageway.

13. A method according to claim d comprising the further step of summingprogressively said product in each channel for all said channels.

14. Apparatus for analyzing particles suspended in a fluid medium whichcomprises:

particle suspension holding means,

a plurality of apertures in fluid communication with said suspensionholding means, each aperture being a different size,

means for moving the fluid medium through the apertures,

transducer means associated with each aperture to produce signals asparticles pass therethrough, said signals being respectivelyproportional to particle volume,

lid

threshold circuit means dividing each transducer output into a pluralityof size channels, each channel having means for accumulating chargeproportional to total particulate volume and deriving a first signalproportional to said accumulated charge,

means for deriving a second signal proportional to the volume of thefluid medium which passed through the aperture of the said transducermeans during the period of time that said charge was accumulated, and

means for dividing the first signal by the second signal to achieve athird signal proportional to the particulate volume concentration.

15. Apparatus according to claim 14 in which means are provided torender said fluid moving means operative for each apertureconsecutively.

16. Apparatus according to claim M in which means are provided todisable all of the channels associated with any aperture after apredetermined length of time so that the duration of signal transducingassociated with each aperture varies directly as the size of theaperture.

t7. Apparatus according to claim 14 in which disabling circuits areprovided for disabling the operation of any given group of channelsassociated with an aperture when the aperture has passed a number ofparticles which produce charge accumulation to :a predetermined signallevel in any one ofa plurality of circuits, including at least saidcharge accumulating means.

1%. Apparatus according to claim M in which the aperture sizes vary fromaperture to aperture by a factor, and

the size ranges of the channels associated with each aperture also varyby the same factor.

19. Apparatus according to claim 18 in which said factor is two to one,and

the channel size ranges progress from aperture to aperture.

210. Apparatus according to claim M in which said aperture sizes differby a factor which causes the percentage of coincident passage ofparticles of the smallest size measured by each aperture to besubstantially the same for all apertures, such that the same particleconcentration can be effectively scanned by all apertures, substantiallyirrespective of the breadth and average size of the particle system.

2H. Apparatus according to claim 24) in which said factor issubstantially two to one in diameter, and

the size ranges of the channels associated with each aperture vary by afactor of substantially two to one by particle volume.

22. Apparatus according to claim M in which a pump circuit is providedin each channel for driving its charge accumulating means,

an inverse time signal accumulating circuit comprises said second signalderiving means,

a reference voltage is connected to said pump circuit and said timesignal accumulating circuit so that the rate of charge accumulating andtime signal accumulating are always inversely proportional to eachother, and

multiplying means connects each charge accumulating means with said timesignal accumulating circuit to define said dividing means and providesan output signal representative of particle volume per unitconcentration irrespective of the amount of time that the aperture ispassing fluid medium.

23. in an apparatus for analyzing a particulate system by the use of atleast one passageway through which a portion of the particulate systempasses and is detected in a manner which produces output signals eachproportional to the volume of each detected particle of said system, theimprovement which comprises:

a plurality of logically parallel electrical channels selectivelyresponsive to receive said output signals according to an incrementationbased upon the amplitude of each output signal,

means for progressively accumulating separately the output signals foreach said channel over a determinable period of time,

means for generating a reciprocal of said period of time, and

means for producing for each channel the mathematic product of saidaccumulated output signal and said time period reciprocal at anyspecific time to obtain the total particulate volume per unit time basedupon said specific time for each channel.

24. Apparatus according to claim 23 further comprising means fordividing the volume of said sample portion by said specific time,thereby yielding the ratio of total particulate volume per channel tovolume of said sample portion.

25. Apparatus according to claim 24 further comprising a referencesignal source coupled to said accumulating means and said generatingmeans for maintaining the relationship between sample portion volume andspecific time constant.

26. Apparatus according to claim 25 further comprising means forterminating the duration of said specific time in response to a presetsignal amplitude in one of said channels.

27. Apparatus according to claim 25 further comprising means forterminating the duration of said specific time in response to improperdetection of said particles.

28. Apparatus according to claim 25 further comprising means forterminating the duration of said specific time in response to anaccumulation of said input signals upon at taining signal capacity ofany one channel.

29. Apparatus according to claim 25 further comprising means forterminating the duration of said specific time in response to a fixedtime measurement.

30. Apparatus according to claim 23 in which a plurality of thepassageways are arranged logically parallel, each having itsinterrelated channels, and

the incrementation of said channels is interrelated in a regularprogression base upon particle volume.

31. Apparatus according to claim 30 further comprising means forenabling said accumulating means for said plurality of channels of anyone passageway in times relationship to the enabling of saidaccumulating means for said plurality of channels of at least one otherof said passageways.

32. Apparatus according to claim 30 further comprising means forregulating the rate of flow of said said sample portion through saidpassageways so that such rate is different for each passageway.

33. Apparatus according to claim 32 in which said regulating means arethe passageways themselves which have their diameters arranged accordingto a mathematic progression.

34. Apparatus according to claim 33 in which there is provided asufficient plurality of passageways and channels per passageway forcausing each passageway to respond to an especially narrow range ofdifferent volumes.

35. Apparatus according to claim 30 further comprising means for summingprogressively said product in each channel for all said channels.

zg ggg UNITEII STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,603,875 p d Sept. 7, 1971 Inventor(s) WALLACE H. COULTER, et a1.

It is certified that errer appears in the above-identified patent andthat said Letters Patent are hereby cerrected as shown below:

Column 11, line 6, change "tee" to --the-'-, line 16 change "by" to"to", line 25 change "means" to --mean--; Column 12, line 65, delete"channels to be selectively responsive to said"; Column 13, line 44,after "in" insert --timed--; Column 16, line 7, change "base" to--based--, line 10 change "times" to --timed--, line 26, afterdifferent" insert --partic1e--.

Signed and sealed this 9th day 01" May 1972.

(SEAL) A 1*; Lest:

DWARD M.FLJ:TCHI:3R,JR. ROBERT GOTTSCHALK 1i tte sting OfficerCommissioner of Patents

1. A method for analyzing a particulate system by the use of at leastone passageway through which a sample portion of the particulate systempasses and is detected, said method comprising the steps of: producingoutput signals each proportional to the volume of each detected particleof said system, passing said output signals to a plurality of logicallyparallel channels, separating said channels to be selectively responsiveto said output signals in channels according to an incrementation basedupon the amplitude of each said output signal, accumulating separatelyand progressively the output signals for each said channel over adeterminable period of time, generating a signal proportional to thereciprocaL of said period of time, and producing for each channel anelectric signal quantity equal to the mathematic product of saidaccumulated output signal and said reciprocal time signal at anyspecific time to obtain an electric signal quantity proportional to thetotal particulate volume per unit time based upon said specific time foreach channel.
 2. A method according to claim 1 comprising the furtherstep of dividing the volume of said sample portion by said specifictime, said step of producing thereby yielding the ratio of totalparticulate volume per channel to volume of said sample portion.
 3. Amethod according to claim 2 comprising the further step of maintainingthe ratio between sample portion volume and specific time constant.
 4. Amethod according to claim 3 comprising the further steps of terminatingthe accumulating step upon the accumulation of a preset signal amplitudein one of said channels.
 5. A method according to claim 3 comprising thefurther step of terminating the duration of said specific time inresponse to improper detection of said particles.
 6. A method accordingto claim 3, comprising the further step of terminating the duration ofsaid specific time in response to an accumulation of said output signalsupon attaining signal capacity of any one channel.
 7. A method accordingto claim 3 comprising the further step of terminating the duration ofsaid specific time in response to a fixed time measurement.
 8. A methodaccording to claim 1, including sending the output signals through aplurality of the passageways arranged logically parallel, eachpassageway arranged to pass the separated output signals through itsinterrelated channels, and arranging the incrementation of all saidseparated output signals in a regular progression based upon particlevolume.
 9. A method according to claim 8 comprising the further step ofenabling said accumulating step for the separated output signals for anyone of said plurality of channels in relationship to the sameaccumulating enabling of the other of said plurality of channels.
 10. Amethod according to claim 8 comprising the further step of regulatingthe rate of flow of said sample portion through said passageways so thatsuch rate is different for each passageway.
 11. A method according toclaim 10 in which said regulating is accomplished by sizing saidpassageways according to a mathematic progression.
 12. A methodaccording to claim 8 comprising the further step of arranging thepassing of the output signals through the passageways such that a narrowamplitude range is sent through each passageway.
 13. A method accordingto claim 8 comprising the further step of summing progressively saidproduct in each channel for all said channels.
 14. Apparatus foranalyzing particles suspended in a fluid medium which comprises:particle suspension holding means, a plurality of apertures in fluidcommunication with said suspension holding means, each aperture being adifferent size, means for moving the fluid medium through the apertures,transducer means associated with each aperture to produce signals asparticles pass therethrough, said signals being respectivelyproportional to particle volume, threshold circuit means dividing eachtransducer output into a plurality of size channels, each channel havingmeans for accumulating charge proportional to total particulate volumeand deriving a first signal proportional to said accumulated charge,means for deriving a second signal proportional to the volume of thefluid medium which passed through the aperture of the said transducermeans during the period of time that said charge was accumulated, andmeans for dividing the first signal by the second signal to achieve athird signal proportional to the particulate volume concentration. 15.Apparatus according to claim 14 in which meAns are provided to rendersaid fluid moving means operative for each aperture consecutively. 16.Apparatus according to claim 14 in which means are provided to disableall of the channels associated with any aperture after a predeterminedlength of time so that the duration of signal transducing associatedwith each aperture varies directly as the size of the aperture. 17.Apparatus according to claim 14 in which disabling circuits are providedfor disabling the operation of any given group of channels associatedwith an aperture when the aperture has passed a number of particleswhich produce charge accumulation to a predetermined signal level in anyone of a plurality of circuits, including at least said chargeaccumulating means.
 18. Apparatus according to claim 14 in which theaperture sizes vary from aperture to aperture by a factor, and the sizeranges of the channels associated with each aperture also vary by thesame factor.
 19. Apparatus according to claim 18 in which said factor istwo to one, and the channel size ranges progress from aperture toaperture.
 20. Apparatus according to claim 14 in which said aperturesizes differ by a factor which causes the percentage of coincidentpassage of particles of the smallest size measured by each aperture tobe substantially the same for all apertures, such that the same particleconcentration can be effectively scanned by all apertures, substantiallyirrespective of the breadth and average size of the particle system. 21.Apparatus according to claim 20 in which said factor is substantiallytwo to one in diameter, and the size ranges of the channels associatedwith each aperture vary by a factor of substantially two to one byparticle volume.
 22. Apparatus according to claim 14 in which a pumpcircuit is provided in each channel for driving its charge accumulatingmeans, an inverse time signal accumulating circuit comprises said secondsignal deriving means, a reference voltage is connected to said pumpcircuit and said time signal accumulating circuit so that the rate ofcharge accumulating and time signal accumulating are always inverselyproportional to each other, and multiplying means connects each chargeaccumulating means with said time signal accumulating circuit to definesaid dividing means and provides an output signal representative ofparticle volume per unit concentration irrespective of the amount oftime that the aperture is passing fluid medium.
 23. In an apparatus foranalyzing a particulate system by the use of at least one passagewaythrough which a portion of the particulate system passes and is detectedin a manner which produces output signals each proportional to thevolume of each detected particle of said system, the improvement whichcomprises: a plurality of logically parallel electrical channelsselectively responsive to receive said output signals according to anincrementation based upon the amplitude of each output signal, means forprogressively accumulating separately the output signals for each saidchannel over a determinable period of time, means for generating areciprocal of said period of time, and means for producing for eachchannel the mathematic product of said accumulated output signal andsaid time period reciprocal at any specific time to obtain the totalparticulate volume per unit time based upon said specific time for eachchannel.
 24. Apparatus according to claim 23 further comprising meansfor dividing the volume of said sample portion by said specific time,thereby yielding the ratio of total particulate volume per channel tovolume of said sample portion.
 25. Apparatus according to claim 24further comprising a reference signal source coupled to saidaccumulating means and said generating means for maintaining therelationship between sample portion volume and specific time constant.26. Apparatus according to claim 25 further comprising means forterminating the duration of said specific time in response to a presetsignal amplitude in one of said channels.
 27. Apparatus according toclaim 25 further comprising means for terminating the duration of saidspecific time in response to improper detection of said particles. 28.Apparatus according to claim 25 further comprising means for terminatingthe duration of said specific time in response to an accumulation ofsaid input signals upon attaining signal capacity of any one channel.29. Apparatus according to claim 25 further comprising means forterminating the duration of said specific time in response to a fixedtime measurement.
 30. Apparatus according to claim 23 in which aplurality of the passageways are arranged logically parallel, eachhaving its interrelated channels, and the incrementation of saidchannels is interrelated in a regular progression base upon particlevolume.
 31. Apparatus according to claim 30 further comprising means forenabling said accumulating means for said plurality of channels of anyone passageway in times relationship to the enabling of saidaccumulating means for said plurality of channels of at least one otherof said passageways.
 32. Apparatus according to claim 30 furthercomprising means for regulating the rate of flow of said said sampleportion through said passageways so that such rate is different for eachpassageway.
 33. Apparatus according to claim 32 in which said regulatingmeans are the passageways themselves which have their diameters arrangedaccording to a mathematic progression.
 34. Apparatus according to claim33 in which there is provided a sufficient plurality of passageways andchannels per passageway for causing each passageway to respond to anespecially narrow range of different volumes.
 35. Apparatus according toclaim 30 further comprising means for summing progressively said productin each channel for all said channels.